Top U.S. companies including Google, Microsoft, and Starbucks took the unusual step on Thursday of legally documenting their opposition to the Defense of Marriage Act.

A brief filed in court comes from 70 businesses and organizations that want their voice heard on the constitutionality of DOMA, which bans same-sex marriage from being recognized federally and stops couples married in states such as Massachusetts from having their weddings recognized in less accepting places such as Alabama.

The companies paint the law as an overburdening government regulation that should be repealed.

Their brief points out that the Republican leadership in the House of Representatives is defending DOMA in court on the notion that it imposes "a uniform rule" on whose marriage is recognized. "The perspective of the American employer who must implement DOMA is very different," the companies state. "Employers are obliged to treat one employee spouse differently from another, when each is married, and each marriage is equally lawful."

The companies say DOMA "forces" them "to investigate the gender of the spouses of our lawfully married employees and then to single out those employees with a same-sex spouse." For example, HIPPA laws usually consider marriage a "qualifying event" that automatically enrolls a spouse in an employee's health insurance. Companies now spend time and money weeding out any gay employees who get married.

If companies don't want to discriminate, because it hurts their recruiting efforts or they're just opposed to it in principle, then DOMA causes a bunch of "workarounds" that come with wasteful administrative costs of their own.

Companies complain that when a same-sex couple legally marries, it requires them "to maintain two sets of books." That's because the couple is considered married under state law but not married under federal law. "The double entries ripple through human resources, payroll, and benefits administration," they write.

Some of the companies have had to pay consultants to jury-rig systems used to track benefits and taxes so they can accommodate the double records. "These dual regimes have spawned an industry of costly compliance specialists," they complain.

"The burden on the small employer is especially onerous," the companies point out. Small businesses can't afford to hire consultants, and "such burdens, standing alone, might chill a smaller employer from employing an otherwise qualified employee because she happens to be married to a same-sex spouse."

Read a complete list of companies that signed onto the brief on the next page.